t2021: mark a test as fixed

The failure was fixed by the previous commit.
Signed-off-by: NJohannes Sixt <j6t@kdbg.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t/t2021-checkout-overwrite.sh

@@ -39,7 +39,7 @@ test_expect_success SYMLINKS 'create a commit where dir a/b changed to symlink'
 	git commit -m "dir to symlink"
 '
 
-test_expect_failure SYMLINKS 'checkout commit with dir must not remove untracked a/b' '
+test_expect_success SYMLINKS 'checkout commit with dir must not remove untracked a/b' '
 
 	git rm --cached a/b &&
 	git commit -m "un-track the symlink" &&